Displays in image display devices, such as television devices, are now being shifted from conventional cathode-ray tube displays to thin displays, such as liquid crystal displays and plasma displays. With the thin displays, the thicknesses of the image display devices can be reduced. Liquid crystal panels included in the liquid crystal display devices do not emit light, and thus backlight devices are required as separate lighting devices.
An edge light-type backlight device including a light guide plate with a light entrance surface on the side and light sources such as LEDs arranged opposite the side of the light guide plate is known. Such a backlight device may includes a positioning structure for positioning the light guide plate relative to a chassis that holds the light guide plate therein.
Patent Document 1 discloses an edge light-type backlight device including a positioning structure for positioning a light guide plate. The backlight device includes the light guide plate, LED light sources, and a chassis. The light guide plate has a light entrance surface on aside. The LED light sources arranged opposite the side of the light guide plate. The chassis holds the light guide plate therein. The light guide plate has cutouts in sides thereof. Each cutout has a square U shape in plan view. Projections are provided on side plates of the chassis opposite the cutouts. In the backlight device, the projections on the chassis are fitted in the cutouts of the light guide plate. As a result, the light guide plate is positioned relative to the planar direction thereof.